An elevator cage is usually guided on vertically extending guide rails. In that case it can be important that the sliding guidance or rolling guidance shoes, which are arranged at the elevator cage and guide the elevator cage along the guide rails, do not, as far as is possible, cant relative to the guide rails. By canting there is meant in this context that the elevator cage is inclined in the horizontal relative to the guide rails due to a non-uniform weight distribution and a displacement, which is connected therewith, of the center of gravity of the elevator cage in the horizontal, thus the elevator cage or the cage floor is not arranged perpendicularly or almost perpendicularly to the guide rails. The sliding guidance or rolling guidance shoes are thereby subjected to increased friction, which can lead on the one hand to more wear and on the other hand to greater energy consumption. Compensation for the non-uniform weight distribution of the elevator cage is usually provided by compensating weights arranged at the underside of the elevator cage or in the elevator cage frame.
Elevator cage floors with a composite structure are frequently used in elevator construction. An elevator cage floor of that kind has, inter alia, the function of accepting the weight of the cage superstructure with walls, cage roof, cage doors and diverse fixtures as well as the total maximum rated load and conducting the weight into the cage frame, usually by way of suitable vibration insulating elements. In that case it can be important that the entire floor does not deform beyond certain limits even under eccentric loading, i.e. does not warp or twist. It is equally important that it cannot be excited into impermissibly strong natural bending oscillations due to disturbing oscillations such as are primarily transmitted to the cage from the drive by way of the support cables. This can be achieved by a high degree of bending stiffness of the floor in all directions with a highest possible bending natural frequency resulting therefrom. A further demand on such an elevator cage floor is that its surface, which is usually formed by a steel plate, does not suffer permanent deformations under high loads concentrated on small areas (for example, due to transport equipment with relatively small wheels). Standards of certain European countries additionally prescribe that elevator cages must contain only minimum amounts of materials which are not classified as ‘non-combustible’.
EP 0 566 424 B1 describes a construction of an elevator cage floor in which the requisite characteristics are to be achieved by use of a composite-structure principle (sandwich principle). In that case, a core of wood, cardboard or thermoplastic foam is glued in place substantially between an upper top plate constructed as a composite layer and an equivalent lower base plate. In order to achieve sufficient strength of the top plate, which forms the cage floor surface, relative to loads concentrated on small areas, support webs are inserted between strips of the core material. In order that cage parts such as, for example, cage walls or door thresholds connected with this floor can be fixed in place the described composite-structure plate is enclosed by a steel frame.
EP 1004538 B1 describes a cage floor for passenger or goods elevators in composite-structure or sandwich mode of construction, which as core contains a structure, which is similar to a grating, of intersecting longitudinal and transverse slats firmly connected with the base plate and the top plate. Such a cage floor is stiff in bending and torsion and has a high bending natural frequency. If the cage floor consists of steel, then the elements of the composite structure can be connected together by slot welding.
Due to the fact that the mass of an elevator cage floor with a composite-structure core is low as a consequence of the mode of construction, it can happen that the friction at the drive pulley in the drive-pulley elevators is too small and twisting of the support means at the drive pulley thereby arises. In order to counteract that, the elevator cage is frequently weighted with appropriate weights at the underside of the elevator cage or in the elevator cage frame. In order that these weights can be mounted on the underside of the elevator cage, an additional frame or an additional component is frequently necessary.